Armor plate



Nov. 17, 1964 M, BALLU 3,157,090

ARMOR PLATE Filed Feb. 9, 1961 FIG. 1

FIG. 2

INVENTOR. LOUIS HENRI BALLU BYWZJZQ W 774% ATTORNEYS 3,l57,090 PatentedNov. 17, 1964 3,157,090 ARMOR PLATE Louis Henri Denys Marie Ballu,Epernay,

Qharnpiieury, France Filed Feb. 9, 1961, Ser. No. 38,012 (Iiaims. (81.89-36) Improvements to conventional weapons and the development of thenuclear weapon increase both the diversity and the magnitude of thehazards to which personnel are exposed.

It is consequently necessary that a given material should still bettersatisfy certain criteria already required for withstanding conventionalWeapons, that it should ensure maximum weight-saving to facilitatemobility in operational zones and that it should be designed to meet newcriteria such as those arising from atomic radiation, for example.

As regards projectiles used by infantry, of which subversive warfaretends to increase utilization and hence also the lethal effects in allprobability, systematic tests have shown that such projectiles can bestbe stopped by very hard steels when high impact velocities are involved,and that the fragility factor becomes preponderant at velocities of theorder of those associated with small arms.

Furthermore, the steel cores used in perforating projectiles have shownliability to fragmentation when they encounter armor of greater surfacehardness than their 0WD. 1

On the other hand, very hard steels present considerable machining andassembling difiiculties and display a degree of fragility againsthigh-momentum projectiles and blast effects, and are apt to fatiguethrough the vibration set up by the iring of automatic weapons or bydrive, transmission or propulsive components, etc., since certainstructural parts can be subjected to very high frequencies due to thefact that such steels will vibrate at the higher harmonics duringsustained vibration, or

can be subjected to beats.

When structural and assembly components are produced, as is often thecase, from steels difiicult to machine, this notably results in a largeWeight penalty being incurred, as well as local stresses and a certainstructural fragility.

Armor plate consisting of layers of differently processed or differentgrades of steel offer no machining advantages and their performance hasnot justified their general use. i

Armor plate made of the known light alloys is incapable in certaincasesgenerally when residual velocities exceed 1,000 fps-of offering aperformance comparable to that of steel; on the other hand, performance,

, assessed in terms of weight of metal per unit of protected area, is inthe vast majority of cases superior at velocities below 1,000 f.p.s.

Other objects and many of the attendant advantages of the invention willbe readily appreciated as the same becomes better understood byreference to the following description, when considered with theaccompanying drawing wherein:

FIGURE 1 shows in cross-section a composite armor constructed inaccordance with the invention; and

FIGURE 2 is a perspective view of a pre-armor plate.

Broadly, thearmor plate according to this invention is intended forstrongpoints in fixed installations, vehicles, ships, etc., and ischaracterized in that it consists of an inner metal armor plate ofeasily machinable light alloy of suitable mechanical characteristics toform the walls of the shell or element to be shielded, and in anexternal pre-armor plate 11 of very hard steel of high elastic limit andsufficiently thick to reduce the velocity of the projectiles which thearmor is designed to withstand and to render that velocity low enough sothat, after perforating said pro-armor plate, theprojectiles aretravelling at a velocity low enough for it to be nullified within thethickness of the inner or structural armor plate 10.

These functional components of the armor as a whole are joined togetherwith a layer 12 of cold-vulcanizing elastomer glue, or similar means,after said components have been machined separately by the method mostsuitable to each, and notably after the complete inner armor plate 10has been assembled by some appropriate means such as welding inparticular.

Machining and assembly of the light alloy shell 10 raises nodiificulties and results in no parasite overbur dening that does notcontribute to protection. Consequently, such a shell can be made tightand the fittings for the necessary mechanical components secured theretoby drilling, tapping and welding.

It will be preferable, in particular, not to fit the prearmor plate 11before the remainder of the system has been finished and, wherenecessary, tested, and to design said pro-armor plate 11 is sufficientlysmall elements to ensure rational shell architecture, facilitate theexpansion permitted by the elastomer joint 12 and reduce the unit weightof the elements to facilitate assembly operations or replacements afterperforation.

Such an arrangement assists weight-saving in particular, by permittingas accurate a distribution as required of the thicknesses called for byoperational needs or degree of exposure to, fire.

The outer armor plates or scales constituted thus may be bevelled asshown at 13 to facilitate lapping, with due account for angles settingsmost vulnerable to projectile impact angles.

Detachment of the scales, to permit local repairs say, can be achievedfor example by injecting a fluid, solvent if necessary, under pressure,with a needle inserted between the pre-armor and the structural armor orpassing straight through the latter which is easy to drill and tap toform a hole such as 14.

Pre-armor plate of weight and efficacy differing ac cording to themissions for which the equipment is destined may be provided on a givenproduction-type vehicle body or gun turret.

From the operational standpoint, the weight saving enables dangerousareas and obstacles to be crossed more rapidly and facilitates airtransport.

Eflicacy of the protection is broadened against:

(1) Anti-personnel or perforating projectiles possessing high kineticenergy, by the provision of successive materials suitable for theresidual velocities and for increasing the likelihood of core rupture.

(2) Heavy splinters and projectiles capable of rupturing the pre-armorby high-momentum impact but which expend their energy in deforming themore ductile structural armor plate.

(3) The effects arising from the projection of armorplate or projectilesplinters, the latter being arrested by the inner armor plate.

(4) Blast effects, by reason of the great rigidity of the plates, theresistance to fiexure of which for a given weight is high, while thegrain flow is virtually neutral in the vicinity of the elastomer.

(5) Combined blast and splinter effects (grenades and shells), as isevident from the previous two paragraphs.

(6) Rupture due to fatigue, vibration being damped by theheterogeneousness of the medium and the hysteresis of the elastomer.

(7) Heat effects from nuclear devices: for a given mass, the heatconductivity per unit area of steel is 35% higher than that of aluminum.The coefiicient of conductivity of the elastomer is half that of thesteel, yet its small thickness introduces a dual convection effect. (8)Gammaradiation, for whereas the half-value thicknesses of the steel andthe light alloy are substantially inversely proportional to theirdensities, it is a wellknown fact that alloy steels exposed to gammaradiation become radioactive in turn, whereas light alloys decontaminaterapidly.

The armor according to the invention can be made by a methodcharacterized in that the component parts of the inner armor plate andthose of the outer armor plate are machined separately and assembled insitu after their joining faces have been smeared with the aforementionedelastomer glue, or assembled by some similar means. It is to beunderstood that the invention is by no means limited to the embodimentsdescribed and illustrated hereinabove by way of example only.

What I claim is:

1. A method of making an armor, said method comprising the steps offorming an inner shell structure of easily machinable light alloy,machining separately plates of extra-hard steel having high elasticstrength, bevelling the edges of said plates, and fastening said plateson the outer face of said inner shell structure by means of an elastomercement compound to obtain an outer pre-armor plating upon said innershell structure.

2. A composite armor adapted to withstand the impact of high-velocityprojectiles, comprising an inner shell of easily machinable light alloyhaving suitable mechanical characteristics, a plurality of outerpre-armor plates of extra-hard steel having high elastic strength and alayer of self-vulcanizing elastomer cement interposed between said innershell and said outer pre-armor plates, the thickness of the latter beingsufiicient to reduce the velocity of said projectiles, so that theprojectile velocity is low enough after one of said pre-armor plates hasbeen perforated to allow said projectile to have its velocity nullifiedwithin the thickness of said inner shell.

3. A composite armor according to claim 2, wherein said outer pre-armorplates are fully machined while independent of each other, before. finalassembly onto said inner shell. I

4. A composite annor according to claim 3, wherein said pre-armor plateshave bevelled registering edges to facilitate their overlapping.

5. A composite armor according to claim 2, wherein orifices are provided.in said inner shell for injecting under pressure a solvent of saidelastomer cement to dismount at least one of said outer pro-armorplates.

References Cited in the file of this patent UNITED STATES PATENTS1,270,871 Rixson July 2, 1918 1,510,243 Perry Sept. 30, 1924 1,995,484Sullivan Mar. 26, 1935 2,132,324 Schrank Oct. 4, 1938 2,410,022 DumaisOct. 29, 1946

1. A METHOD OF MAKING AN ARMOR, SAID METHOD COMPRISING THE STEPS OFFORMING AN INNER SHELL STRUCTURE OF EASILY MACHINABLE LIGHT ALLOY,MACHINING SEPARATELY PLATES OF EXTRA-HARD STEEL HAVING HIGH ELASTICSTRENGTH, BEVELLING THE EDGES OF SAID PLATES, AND FASTENING SAID PLATESON THE OUTER FACE OF SAID INNER SHELL STRUCTURE BY MEANS OF AN ELASTOMERCEMENT COMPOUND TO OBTAIN AN OUTER PRE-ARMOR PLATING UPON SAID INNERSHELL STRUCTURE.